BACKGROUND: Because the proportion of elderly patients admitted to the intensive care unit (ICU) is increasing, the objective of this study was to test the hypothesis that very elderly patients with better preadmission functional status would have better medium-term survival and functional status after an ICU stay.METHODS: In this observational study, 96 patients (68% surgical and 32% medical) aged ≥80 years and admitted to the ICU between May 2008 and June 2009 were recruited. Functional status was assessed using a modified Katz Scale and the Lawton Scale. Primary outcomes were: one-year mortality and its independent predictive factors, one-year functional status and perceived quality of life.RESULTS: Multivariate analysis showed that type of admission (surgical vs. medical), existence of cancer, Sequential Organ Failure Assessment (SOFA) Score at ICU admission and occurrence of septic complications during the ICU stay were independent predictive factors for one-year mortality, but preadmission functional status was not. At one year, despite functional decline in 50% of survivors, 68% perceived their health status to be equivalent to or better than before and 82.6% would agree to a further ICU stay.CONCLUSION: One-year mortality of very elderly patients after an ICU stay is not related to preadmission functional status but to the type of admission, existence of cancer, SOFA Score at ICU admission and occurrence of septic complications during the ICU stay. Despite functional decline in half of these patients, one year after admission 82.6% would agree to another ICU stay.